Double patterning is a technology developed for lithography to enhance feature density in semiconductor manufacturing. Lithography is typically implemented in which a photoresist is applied to a surface of a semiconductor wafer, and then patterns are defined in the photoresist. The patterns in the patterned photoresist defined in a lithographic mask and are implemented as a transparent portion or an opaque portion. In double patterning, two photolithography processes are performed on a single layer to overcome the optical proximity effect, which can lead to two features to blend into one another causing a short.
Self-aligned double patterning (“SADP”) is a semiconductor process designed to reduce the number of photolithography steps needed to develop a single layer. SADP utilizes the creation of hard mask spacers to create additional patterns not formed in photolithography masks. The pattern created by the spacers are etched and filled to create additional patterns in the semiconductor substrate without the use of additional lithographic masks.